Prosthetic eye devices are known in the art and can be configured to partially or completely replace an eye, e.g., a human eye for the aesthetic purpose of providing a more normal appearance. People can require use of such prosthetic eye device arising from a variety of reasons, such as an accident, disease or birth defect. Thus, the type of prosthetic eye device that is used can and will vary in its design depending on the particular application. In the case where the entire eye is being replaced, or a case where a frontside portion of the existing eye is being complemented, the prosthetic eye device can include an iris portion that is constructed to replicate the appearance of a natural eye, e.g., to replicate the appearance of the iris of the patient's existing eye. The iris portion of the device preferably comprises a complex colored and patterned portion that extends concentrically around the pupil portion of the eye to the sclera or white portion of the eye.
Prosthetic eye devices, e.g., in the form of a replacement or artificial eye, are conventionally made from materials such as methyl methacrylate and comprise an iris assembly positioned at a frontside portion of the eye device that is intended to replicate the color and patterning of a natural eye. The iris assembly is formed from a composite construction of individual elements. Typically, the iris image, depicting the complex color and patterning of the eye, is provided on a flat disk-shaped rigid plastic element.
The most difficult and time-consuming part of making a prosthetic eye device comprising an iris assembly is duplicating the iris of the patient's natural eye, as humans have a complex multicolored and patterned iris that can vary significantly from person to person. To achieve realistic color and pattern matching it has been the conventional practice to make the entire iris image by the time-consuming process of hand-painting the color and pattern of the iris in a manner matching the person's existing eye onto a piece of plastic by hand. In order to obtain the desired color intensity of the iris, oil-based paints are often used or mixed with acrylic paints.
An alternative method of replicating the iris portion of the eye for use in a prosthetic eye device involves a process of printing onto a flat sheet of photographic film or photographic paper a basic color of an iris. In this method, the basic color of an iris is printed by a conventional screen printing technique onto the flat piece of photographic film or paper as a starting point, then the film or paper is placed on a flat disk-shaped plastic element. The basic color is selected to generally match the underlying color of the patient's iris. The desired iris image matching the patient's eye, comprising the complex arrangement of coloring and patterning, is then provided by hand painting over the printed base color. This method was thought useful for potentially minimizing the amount of hand painting required during iris assembly formation by providing a basic colored foundation.
While the above-described photographic technique was helpful in reducing the amount of time necessary to create the iris image by reducing the amount of initial hand painting, this technique is not without its problems. For example, during subsequent steps in making the prosthetic eye device, the iris image can become distorted. This occurs because the subsequent processing steps involved in making a prosthetic eye device involves exposing the iris image to adhesives having strong solvents. The presence of these solvents is known to cause the image captured on photographic film or photographic paper to be dissolved or otherwise distorted.
There are known disadvantages to the above-described conventional methods of making the iris assembly for use in a prosthetic eye device. A first disadvantage relates to the current practice of placing the iris image onto a flat substrate, e.g., a disk-shaped plastic element, whether the iris image is created entirely by hand painting or by the hybrid process of hand painting over the printed base color. In either technique the iris image is flat and placed on a flat substrate. In many applications the prosthetic eye device is made to complement an existing portion of a patient's eye or ocular implant. This type of fitment often requires that a backside surface portion of the prosthetic eye device, e.g., a portion that includes a backside surface of the iris assembly, be configured having a nonplanar, e.g., a concave geometry. Conventional iris assemblies comprising an iris image placed on a flat or planar substrate are not well suited for this type of prosthetic eye device application because they do not permit surface shaping. Another disadvantage associated with conventional iris assemblies comprising a flat iris image is that, while appearing normal from a front-facing view, the iris image does not appear normal-looking from a side view.
Another known disadvantage associated with the above-described methods of making an iris assembly relates to the current practice of having to paint either the entire iris image, or a portion of the iris image, by hand. Since the color and pattern of a person's iris is unique and may be quite complex, the process of painting the entire iris image by hand involves a time-consuming practice of starting from scratch each time. The time spent in creating the desired iris image is reduced somewhat by using the screen printing technique. However, because the screen printing technique still involves some amount of hand painting, it is still time consuming. Additionally, in either technique, once the iris image is painted it may take many iterative steps of modifying the initial image to perfect the look of the iris in the completed iris assembly. Oftentimes it is less time consuming to start from scratch rather than to modify an existing image.
Another disadvantage relates to the current practice of using oil-based paints to provide the desired iris color intensity. It is known that the use of such oil-based paints have a coefficient of expansion that is different than that of the surrounding monomeric or polymeric materials that are used to form the remaining components of the iris assembly. Because a prosthetic eye device is exposed to moisture when worn and to repeated cycles of wetness and dryness, it is theorized that the different coefficients of expansion between the adjacent members in the iris assembly are responsible for delamination of such members, whereby the painted paper member becomes separated from adjacent iris assembly components. This delamination is not desirable as it makes the iris portion of the prosthetic eye appear cloudy or distorted, ultimately requiring replacement.
Another disadvantage also relates to the current practice of hand painting the iris image and using oil-based paints to provide the desired iris color and pattern onto the plastic element. During the process of making the iris assembly, after the iris image is painted on the plastic element, a clear lens cover or cornea piece is placed over and adhered to the painted surface of the plastic element using a suitable adhesive. During the step of adhering the front cover to the iris image plastic element it is sometimes necessary to move the front cover vis-à-vis the plastic element to provide a desired complementary fit. During this step it is known that the painted iris image can smear or otherwise become distorted, thus rendering the iris element useless and requiring that a new iris element be painted. As mentioned briefly above, this unwanted distortion of the iris image during attachment of the cornea piece of the assembly is also known to occur when using an iris image formed by photographic technique described above due to the interaction of solvents in the adhesive with the chemicals in the photographic film or photographic paper.
It is, therefore, desired that an iris assembly be constructed for use in a prosthetic eye device in a manner that increases the overall efficiency of making the iris assembly and the prosthetic eye device, e.g., a replacement eye. It is also desired that the iris assembly be constructed in a manner that: (1) enables use of the same in applications calling for a nonplanar fitment of a prosthetic eye device with an adjacent portion of a patient's eye or ocular implant; (2) provides a normal appearing iris from both front and side views; (3) minimizes or eliminates the potential for iris assembly delamination; (4) minimizes or eliminates the potential for unwanted distortion of the iris image during iris assembly construction; and (5) minimizes or eliminates the need to start from scratch when changing or modifying the iris image during iris assembly construction.